A wide variety of manual knife sharpeners have been used for centuries, but most of these have been disappointing because they did not provide a precise means to control the sharpening angle. The importance of angle control to the creation of ultra sharp knife edges is recognized in, for example, U.S. Pat. Nos. 5,390,431 and 4,627,194.
Manual sharpeners have been described by others where control of the sharpening angle is obtained by use of clamping devices or blade carriers in which the blade is mounted in a mechanism and physically restrained so that the facet of the blade edge is restrained to remain parallel to the abrasive sharpening surface as the clamping device or carrier is moved in a predetermined direction relative to the abrasive sharpening surface. A major disadvantage of using such clamping devices or carriers to control sharpening angle is the awkwardness and inconvenience of the devices themselves.
One example of such blade carriers, U.S. Pat. No. 2,652,667 by C. D. Arnold, describes a sharpener where the blade is placed in a knife blade holder which moves in a direction parallel to the surface of the sharpening stone while the blade facet is in contact with the abrasive stone. The blade is wedged into the blade holder that sets the blade at a predetermined angle to the abrasive surface. Another example, is U.S. Pat. No. 3,882,642 by C. S. Sykes which describes a different knife holder that moves in a direction parallel to the surface of the sharpening stone. The blade is held in fixed nonsliding contact with the holder as the holder is moved in a direction parallel to the abrasive surface. As the holder moves the knife edge moves with it in contact with the abrasive surface.
There has been a plethora of manual sharpeners ranging from sharpening stones and manuals steels to more modern sharpeners such as described in U.S. Pat. No. 5,477,753 that provide no means to control accurately the angle between the plane of the edge facet and the abrasive surface at their point of contact.